Mechanisms underlying normal human retinal development and dystrophies are still not fully understood, despite the fact that more than half of Americans who become blind each year are diagnosed with some genetic defect. Elucidation of events in normal retinal development may allow us to understand the basis of dystrophies and their better management. Most of the information available on human retinal development emanates from avian of rodent models and few human studies are limited to tumor cell lines. No long term studies are currently possible due to limited sampling of progenitors and senescence that ensues in primary cultures. We propose an alternative strategy that will enable us to perform long term studies. The objective of this proposal is to establish age-restricted cell lines from developing (4, 8, 12 months fetal) human retinal tissues by SV-40T gene transfection and elucidate events in nearly retinal development in homogenous cell populations. We have already established a retinal cell line (Dutt et al 1994, 1996). It is accepted that retinal cells are multi- potential but is this capacity age dependent? The key questions we propose to ask: a) are the factors that determine cell fate intrinsic to progenitors and change developmentally, b) are cellular and molecular changes in micro environment of progenitors specific for cell fate decisions? We propose to test the hypothesis that cell lines generated from different ages will be developmentally restricted and will vary in their ability to generate different combinations of cells either due to 1) changes in endogenous signals (lineages), 2) changes in exogenous signals, or 3) changed ability of the progenitors to respond to signals (interaction between exogenous and endogenous cues). In this study, using cellular and molecular approaches, we will determine the role of lineages versus extracellular signals in retinal development. We propose to accomplish the following aims: 1) Establish age restricted cell lines from human developing retina by SV-40T gene transfection. 2) Determine cell lineages in progenitors from different ages to determine the role played by endogenous signals. 3) Determine the role of endogenous and exogenous signals and how they interact in cell fate determination.